In the prior '429 patent, a heated handgrip for a vehicle, such as a recreational vehicle, snowmobile, motorcycle and the like, is disclosed in which a wire heating element extends throughout spiral grooves in a land and groove configuration formed on the exterior of a tubular core or sleeve.
A complementary sheath overlays the sleeve and forms the exterior of the handgrip and defines the portion of the grip which is grasped by an operator.
It has been found that although the handgrip disclosed and claimed in the '429 patent is operative, there are certain deficiencies therein.
For example, since the sleeve and the sheath have mating helical land and groove configurations, i.e., spiral lands and grooves or the exterior of the sleeve mating with complementary spiral lands and grooves on the interior of the sheath, there is a tendency for the sheath to separate from the sleeve.
That is, the sheath rotates relative to the sleeve in the fashion of a jackscrew with the result that the sheath and sleeve are displaced relative to one another. Obviously this occurrence is undesirable because it degrades the utility of the grip. Furthermore, since screw action disturbs the placement of the heating wire, there is a danger of short circuits.
In addition, it is desirable to have the resistance wire thoroughly sandwiched between the grooves of the sleeve and the lands of the sheath.
That is, the sleeve is usually molded in a separate operation of a thermoplastic material such as (but not limited to) acrylonitrile-butadiene-styrene copolymer or nylon. Thereafter the resistance wire is wound upon the sleeve. Following that step, the sheath is molded about the wired sleeve using a vulcanizable elastomeric material such as (but not limited to) compounded polymers or copolymers of butadiene or neoprene which create a comfortable grip.